Melanoma has a tendency to metastasize early; however, diagnosis can be difficult due to the overlap in clinical and histologic appearances of melanomas with highly prevalent benign melanocytic nevi (moles). Furthermore, detection of melanoma recurrence remains challenging, as no blood-based marker with sufficient diagnostic accuracy is available. A critical need exists to develop sensitive and specific biomarkers for both early melanoma diagnosis and to detect early recurrences. Recent studies have reported highly recurrent somatic mutations restricted to a narrow region of the telomerase reverse transcriptase (TERT) gene promoter in 38% of primary and 70% of metastatic melanomas. Importantly, if TERT mutations can be shown to be specific for melanoma compared to benign nevi (moles), they may serve as molecular markers for melanoma diagnosis. Moreover, if TERT promoter mutations persist in metastatic melanomas and mutated DNA is shed into the serum, these mutations could also serve as sensitive serum biomarkers for metastatic disease burden. The primary aims of this proposal are to: (1) Screen a well-characterized and diverse set of 100 formalin-fixed paraffin embedded (FFPE) primary melanomas from melanoma patients and 88 non-malignant nevi with varying histologies for TERT promoter mutations using DNA sequencing to determine if these mutations are specific for melanoma, and (2) Using existing, matched FFPE metastatic melanomas and serum samples from metastatic melanoma patients (n=40) and serum samples from nevus-only controls (n=40), determine whether TERT mutations are detectable in serum from TERT mutation-positive metastatic melanoma patients, but not in serum from controls. The impact of our study would be to carry out the initial steps toward developing TERT as a biomarker for molecular pathology diagnosis of melanoma and as a serum biomarker that could be utilized for detecting early relapse or therapeutic response in future epidemiologic and clinical translational studies, ultimately leading to better patient monitoring and more favorable melanoma outcomes.